Withe the advent of Excel 2010 several improvements been in place:
From working in split mode View -> Split
Viewing two workbooks at the same time View -> View Side by Side
In dual head/monitor mode you can also view the same workbook in two Excel windows at the same time, thus fully utilising the dual heads at the same time for the same workbook (same sheet or different).
Using the new window View -> New Window you can have multiple instances of the same workbook open across for your *use*
You can do your VBA coding on one head too and have the Worksheet too on another head
* head = monitor